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  <title>返回前一个 Throwable</title>
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  <div id="layout-content"><div id="exception.getprevious" class="refentry">
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  <h1 class="refname">Exception::getPrevious</h1>
  <p class="verinfo">(PHP 5 &gt;= 5.3.0, PHP 7, PHP 8)</p><p class="refpurpose"><span class="refname">Exception::getPrevious</span> &mdash; <span class="dc-title">返回前一个 Throwable</span></p>

 </div>
 
 <div class="refsect1 description" id="refsect1-exception.getprevious-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="modifier">final</span> <span class="modifier">public</span> <span class="methodname"><strong>Exception::getPrevious</strong></span>(): <span class="type"><span class="type">?</span><span class="type"><a href="class.throwable.html" class="type Throwable">Throwable</a></span></span></div>

  <p class="para rdfs-comment">
   返回前一个 <span class="classname"><a href="class.throwable.html" class="classname">Throwable</a></span> （传递给 <span class="methodname"><a href="exception.construct.html" class="methodname">Exception::__construct()</a></span>方法的第三个参数）。
  </p>
 </div>

 
 <div class="refsect1 parameters" id="refsect1-exception.getprevious-parameters">
  <h3 class="title">参数</h3>
  <p class="para">此函数没有参数。</p>
 </div>

 
 <div class="refsect1 returnvalues" id="refsect1-exception.getprevious-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   返回异常链中的前一个异常 <span class="classname"><a href="class.throwable.html" class="classname">Throwable</a></span>，否则返回<strong><code>null</code></strong>。
  </p>
 </div>


 <div class="refsect1 examples" id="refsect1-exception.getprevious-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-371">
    <p><strong>示例 #1 <span class="methodname"><strong>Exception::getPrevious()</strong></span>示例</strong></p>
    <div class="example-contents"><p>
     追踪异常，并循环打印。
    </p></div>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">MyCustomException&nbsp;</span><span style="color: #007700">extends&nbsp;</span><span style="color: #0000BB">Exception&nbsp;</span><span style="color: #007700">{}<br /><br />function&nbsp;</span><span style="color: #0000BB">doStuff</span><span style="color: #007700">()&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;try&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;</span><span style="color: #0000BB">InvalidArgumentException</span><span style="color: #007700">(</span><span style="color: #DD0000">"You&nbsp;are&nbsp;doing&nbsp;it&nbsp;wrong!"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">112</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;catch(</span><span style="color: #0000BB">Exception&nbsp;$e</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;</span><span style="color: #0000BB">MyCustomException</span><span style="color: #007700">(</span><span style="color: #DD0000">"Something&nbsp;happend"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">911</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$e</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />}<br /><br /><br />try&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">doStuff</span><span style="color: #007700">();<br />}&nbsp;catch(</span><span style="color: #0000BB">Exception&nbsp;$e</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;do&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"%s:%d&nbsp;%s&nbsp;(%d)&nbsp;[%s]\n"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$e</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">getFile</span><span style="color: #007700">(),&nbsp;</span><span style="color: #0000BB">$e</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">getLine</span><span style="color: #007700">(),&nbsp;</span><span style="color: #0000BB">$e</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">getMessage</span><span style="color: #007700">(),&nbsp;</span><span style="color: #0000BB">$e</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">getCode</span><span style="color: #007700">(),&nbsp;</span><span style="color: #0000BB">get_class</span><span style="color: #007700">(</span><span style="color: #0000BB">$e</span><span style="color: #007700">));<br />&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;while(</span><span style="color: #0000BB">$e&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$e</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">getPrevious</span><span style="color: #007700">());<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents"><p>以上例程的输出类似于：</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
/home/bjori/ex.php:8 Something happend (911) [MyCustomException]
/home/bjori/ex.php:6 You are doing it wrong! (112) [InvalidArgumentException]
</pre></div>
    </div>
   </div>
  </p>
 </div>

 

 <div class="refsect1 seealso" id="refsect1-exception.getprevious-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="methodname"><a href="throwable.getprevious.html" class="methodname" rel="rdfs-seeAlso">Throwable::getPrevious()</a> - 返回先前的 Throwable</span></li>
   </ul>
  </p>
 </div>

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